Telephone and the like



Nov. 6, 1928.

H. J. ROUND TELEPHONE AND THE LIKE Filed Jan. 1925 2 Sheets-Sheet -1 mvENmR HENRY J. mum;

av g mmRMEY Nov. 6, 1928. 1,690,840

H. J. ROUND TELEPHONE AND THE LIKE Fil ed Jan. 1925 2 sheets-sheet 2 cm. 0F.

DIAPHRAGM- lNVENTOR new J. aouuo m y (M ATTORNEY Patented Nov. 6,1928.

UNITED STATES HENRY JOSEPH ROUND, OF LONDON, ENGLAND, ASSIGNOB TO RADIO CORPORATION OF AMERICA, 'A CORPORATION OF DELAWARE.

TELEPHONE AND THE LIKE.

Application filed January 3, 1925, Serial No. 484, and in Great Britain January 5, 1924.

This invention relates to telephones and the like and its primary object is to provide an improved loud speaker.

My applicationSerial No. 749.118 filed November 11, 1924, describes a telephone or the like in which the force is applied to the edge of the diaphragm preferably through a coil wound upon a cylindrical flange on the diaphragm and extending into the annular air gap of a magnet.

According to this invention I make the diaphragm of a telephone or the like of annular form and mount it on rubber or other like elastic material, this rubber being gripped a short distance from the annular ring both on the outside and inside of the ring, while force is applied to the diaphragm at the mean of the internal and external diameters of the diaphragm.

The ring diaphragm is preferably formed of non-magnetic material such, for instance, as ebonite, and carries a cylindrical flange which lies in the ring shaped air gap of a magnet and which carries the coil through which the telephone currents are passed.

An equivalent of elastic material would be helical springs loosely covered with a material impervious to air, such as oiled silk, in order to seal the air gap. I

Alternatively, the ring diaphragm may be formed of iron in the usual way.

When such a ring diaphragm is used in conjunction with a horn to form a loud speaker I preferably place in the middle of the -horn and against the substance which fills up the central hole of the diaphragm a .body which blocks up a large part of the interior of the horn, leaving an annular air chamber between it and the horn.

The invention is illustrated in the accompanying drawing, in which Figure 1 is a plan and Figure 2 a section of one -embodiment of the invention, Figure 3 shows a modified form of diaphra m while Figure 4 shows'a diaphragm app ied to a born to form aloud speaker. Figures 5 and 6 show alternative means for actuating the diaphragm. Figure 7 shows, an alternative method of supporting the diaphragm.

Referring to Figs. 1, 2 and 4, 1 is a ring diaphragm of-non-magnetic material, such as cardboard, which carries a cylindrical flange 2, while 3 is the coil through which the telephone currents are passed. Ring 1 is mounted onel'astic material 4 secured to rings 5 and 6, or it may be sup orted by a. series of springs as shown in Figure 7, in which case the air gap is closed by a thickness of some air proof material such as oil silk. Flange 2 is preferably attached to ring 1 by astrip of silk provided with a series of cuts to form tongues turned alter- PATENT OFFICE. v I

nately to each side of the uncut portion, and

sticking the tongues to ring 1 and the uncutportion to flange 2, then smearing the whole including the coil with bakelite varnish and then bakelizing. p The ring diaphragm l is preferably such that any natural frequency it has is high and it may take the form, for example, of a cardboard ring half an inch wide and one thirtysecond of an inch thick, or of a ring of aluminum gauze made air roof with paper.

The same high natural frequency may also be obtained together with the advantage of having a larger diaphragm by making the ring wider and corrugating 1t radially or sticking radial strips on it, or the ring (corrugated or otherwise) may be of V section or of double V section.

The weight of conductor in coil 3 should be preferably 'of the same order as the weight of the diaphragm or a little greater, while the top of flange 2 may be connected at intervals to both edges of the ring 1 by ribs so as to increase the rigidity of the system.

When the diaphragm is large with respect to the magnet the cylindrical flange 2 is situated at the top' of the conical tube whose base is connected to the diaphragm, as shown in Fig. 5, or again when a magnet of the type described in m application above re erred to is not emp oyed a mag netic system, such as a reed or balanced arm telephone system or a gramophone needle, may be secured to the apex of a cone whose base is secured to the diaphragm, the. base of the cone being arranged to bisect radially the ring diaphragm, asshown in Fig. 6.

. The elastic material supporting the ring diaphragm should preferably be stretched tosuch a degree as to communicate to the system when vibrating a low frequency, say, about cycles or v somewhat above, but preferably not above 150 cycles; it has been found that if the materialis not stretched but flabby (in other words too flexible) whereby the natural period becomes very low, the amplitude of the diaphragm for low musical tones will be such that the diaphragm may hit the magnet poles. Such low tones may be produced not only by the sounds transmitted but by the overloading of the low frequency amplifier.

Referring to Figure 3, similar parts are marked with similar figures of reference. The diaphragm 1 conveniently made of cartridge paper is here of double V section, while 11 is a strengthening ring. The magnet system M -is of the type shown in my previous application.

Referring to Figure 4, 7 is the horn of a loud speaker and 8 is a body abutting against ring 6 and filling up the middle of the horn.

Having described my invention what I claim is:

1. In an acoustic device an annular diaphragm, elastic material supporting said diaphragm, supporting means to which said elastic material is secured, actuating means for actuating said diaphragm, and means connecting said actuating means to said diaphragm at the mean portionthereof.

2. In an acoustic device a non-magnetic annular diaphragm, elastic material supportwhich said elastic material is secured, and means for actuating said diaphragm, said actuating means comprising a cylindrical flange carried by said diaphragm, and an armature coil mounted thereon.

3. In an acoustic device an annular dia phragm, elastic material supporting said diaphragm, supporting means to which said elastic material is secured, actuating means for actuating said diaphragm and means connecting said actuating means to said diaphragm at the mean portion thereof, the said elastic supporting material being so adjusted that the amplitudes of movement of the diaphragm for the lowest tones reproduced do not exceed the amplitude of movement which is obtained at the frequencies of about 80 cycles.

4. In an acoustic device the combination of an annular orifice formed by an annular supporting ring and an inner supporting member, an annular diaphragm mounted in said orifice by means of elastic supporting material secured to said diaphragm and to said supporting ring and inner supporting member, and a horn having in it a conical body abutting said inner supporting member and adapted to divide the interior of the born to form an annular air chamber there- 1n.

5. In an acoustic device an annular diaphragm, elastic material supporting said diaphragm, supporting means to which said 1ng said diaphragm, supporting means to elastic material is secured, said elastic supporting material being so tensioned that the natural period of the system is between 80 and 150 cycles per second.

6. An acoustic device comprising a rigid annular diaphragm, an annular supporting ring spaced externally therefrom, an inner supporting member, and a stretched elastic material stretched between said supporting members and adapted to support said diaphragm.

7. In an acoustic device the combination of supporting means, elastic material associated with said supporting means and an annular diaphragm mounted on said elastic material.

8. In an acoustic device the combination of an annular supporting ring, an inner sup porting member inside of said ring and spaced concentrically therefrom, elastic supporting material stretched between said supporting member and said supporting ring, and an annular diaphragm mounted on said elastic supporting material said elastic supporting material being so adjusted that the natural period of the system so composed, is between 80 and 150 cycles per second.

9. In an acoustic device the combination of an annular supporting ring, an inner supporting member interior of said ring, a thin sheet of elastic supporting material stretched between said supporting ring and supporting member, and an annular diaphragm I mounted on said elastic material between said supporting ring and said supporting member. 7 v

10. In an acoustic device the combination of an annular supporting ring, an inner sup porting member interior of said ring, a hollow annular diaphragm of double-V cross section mounted between said ring and said member, and elastic material'connected to said ring and said supporting member and to said diaphragm to support the latter in position. 1

11. In an acoustic device the cbmbination of an annular supporting ring, an inner supporting member interior of said ring, a hollow annular diaphragm mounted between said ring and said member, elastic material connected to said ring and said member and to said diaphragm to support it in position, a cylindrical projection on said diaphragm, mounted mean of the interior and exterior circumference thereof, an armature coil on said cylindrical projection, and a magnetic field structure so constructed as to enclose said coil in a magnetic field.

HENRY JOSEPH ROUND. 

